The invention relates to a conveyor specialized to convey people, and relates more particularly to a conveyor which may serve as a conventional staircase.
Before discussing the invention in detail it may be helpful to define certain terms.
Turning first to FIG. 1, what may be seen is a staircase 48, defined as a flight of stairs with its supporting framing and balustrade 41. Balusters 40 are shown, which are closely spaced vertical supports for railing 43. The railing 43 with supporting balusters 40 are referred to collectively as a balustrade 41. A fitting is a general term for a short transition piece in a handrail where there is a quick change in the direction of the handrail. A gooseneck 42 is a specific type of fitting designed to transition a stair handrail 43 to a horizontal guardrail 49.
It will be appreciated that balustrades are used not only on staircases but also on balconies. Thus a guardrail may be defined which is the top member of a balustrade system designed to keep people from falling off of an open balcony or staircase.
It will also be appreciated that some staircases are not “open,” that is, some staircases have a wall to one side or both. On a side that is not “open” there is usually provided a handrail, defined as a long narrow band of wood or metal following the slope of a staircase placed at a height where a person can hold it for stability while climbing the staircase. It will be appreciate that sometimes a handrail may also act as a guardrail.
Turning to FIG. 2, treads 45 may be seen, each of which is defined as the upper surface of a step in a stair. The staircase may include risers 44, each of which is a vertical board spanning the space between treads on a staircase. Not all staircases have risers.
For a particular staircase there is a tread rise 46 defined as the vertical measurement from the top of one tread to the top of the next tread in line. Likewise there is a tread run 47 defined as the horizontal distance measured from the front of one tread to the front of the next tread above or below it. The slope of a staircase is defined as the measure of the angle formed by the relationship of rise to run on a staircase. The vast majority of staircases are designed so that the tread run is constant across all of the stairs of the staircase, and so that the tread rise is constant across all of the stairs of the staircase.
It will be appreciated that in some staircases, each tread 55 has a “nose” 51 as shown in FIG. 4. With such treads the tread run 47 is defined as shown, measured from the front of one tread to the front of the next tread above or below it.
Some staircases are built with one or more “stair jacks” or “stringers” 50 (FIG. 3) to which treads and risers are attached.
skilled in the art are also familiar with such terms as a “curved staircase,” defined as a staircase which changes direction using a circular pattern with an inside radius less than twice the width of the individual treads; a “spiral staircase,” defined as a staircase whose treads radiate from one central supporting post or newel; and a “winding staircase,” defined as any staircase which changes direction while walking on individual treads which are tapered along their run. A “newel” or “newel post” can be a post giving additional structural support to a balustrade, or can be the central supporting post of a spiral staircase.
Much attention has been paid in recent years to the problem that some people find it difficult to ascend and descend staircases. Where a building (such as a residence or a commercial building) is being constructed, it is a straightforward matter to plan ahead and to provide escalators or elevators. An escalator is an endless loop of stairs which move upward or downward, with stairs returning to the other end of the escalator in a passageway beneath the staircase. An elevator, of course, requires an elevator shaft. An escalator requires setting aside a substantial volume for its return passageway, extending for some distance below the staircase. The escalator takes up a greater width than the width of the treads. Despite these requirements it is usually a straightforward matter, in the design of new construction, to provide any needed elevator shafts and any needed volumes for escalator return passageways and any needed widths.
It often turns out, however, that the need to accommodate a person who finds it difficult to ascend and descend staircases is perceived only after a building has been built. With such a building it is sometimes impossible, or at least prohibitively expensive, to add an elevator or escalator. In the case of a proposed elevator, it often develops that there is no suitable location for the placement of an elevator shaft. In the case of a proposed escalator which might replace a staircase, it often develops that there is no place to put the return passageway and that the width of an escalator is too great to fit in the width of the stairway that is to be replaced.
In a rented or leased space such as a residential apartment, or in a multitenant setting such as a cooperative or condominium apartment, there is a further difficulty in that even if cost is no object, and even if a location for an elevator or escalator can be found, it may be impossible to obtain permission from the landlord or condominium association to carry out the structural modifications that are required for installation of the elevator or escalator.
Faced with these concerns, the person desiring to accommodate (in an existing building) a person who finds it difficult to ascend and descend staircases often has only a few possible approaches, none of which is fully satisfactory. A typical approach is the installation of a chair and track mechanism. A track (or a set of tracks) is installed along one side of the stairway, and a mechanized chair is set up so that it may ascend and descend the track.
The tracked chair has numerous drawbacks. First, it takes away some of the otherwise usable width of the staircase. Even if every effort is made to minimize the lost width (e.g. if the chair seat can fold upwards for storage) the staircase will lose at least an inch or two of width.
Second, the track needs to be lubricated and the lubricated track is necessarily open (to some extent) so that there is the danger that clothing will be stained after coming into contact with the lubricant.
Third, it will often develop that if a person seeks to use the chair at one end (e.g. the top or bottom) of the staircase, this will happen at a time when the chair is at the other end of the staircase. This means that there must be a “call button” to call the chair to the would-be user, and the would-be user is forced to wait until the chair arrives.
Fourth, the chair track system may interfere with use of the hand rail on the side of the staircase where the track system is installed.
Fifth, not all staircases are well suited to chair track systems. A spiral or curved or winding staircase may rule out a track system due to the curves or the winding. Some two-part staircases go straight to a landing, and then proceed upwards at a different angle such as a right angle; such staircases sometimes rule out a chair track system.
Even a straight staircase may be unsuitable for a chair track system. For example if the staircase has balustrades and guard rails on both sides (i.e. neither side is a wall), it may turn out that there is insufficient structural strength in the balustrade to support the chair track system. Even if one side of the staircase has a wall, it may develop that the wall is unsuitable to support the chair track system, due to lack of sufficient structural strength or lack of suitable points of attachment.
It will also be appreciated that a chair track system may be used by at most one person at a time. This is a problem if one person wishes to ascend at the same time another person wishes to descend. It is also a problem if one person wishes to ascend a few moments after another person has already started to ascend. Finally, it is a problem if, say, two persons wish to ascend at the same time, since the chair does not have two seats.
Finally, and perhaps most importantly for many persons, a chair track system may be psychologically or emotionally or aesthetically undesirable. The chair track system is an extraordinarily prominent signal, incapable of being overlooked, that someone has difficulty ascending and descending stairs. This very signal may be uncomfortable for the persons residing in a home where it is proposed to install such a system. Many persons will find a chair track system to be aesthetically displeasing and may try to postpone or avoid its installation for that reason as well.
For all these reasons, it will be readily appreciated that there has been and is a long-felt need for a mechanism which would simultaneously fulfill several seemingly incompatible aims—a mechanism that is well-suited to helping people get from one level of a building to another, that is readily installed even in existing buildings, that can accommodate not only straight staircases but staircases which turn or go around corners, that is likely to be approved by a landlord or condominium association, that does not require structural modifications to the building, that does not take up otherwise usable width of a staircase, that will not make a person wait while it traverses the length of a staircase, and that is not visually intrusive.